What is the intestine?
The intestine is the main part of the digestive system. It starts at the pylorus (stomach gate), leads to the anus and is divided into the slimmer small intestine and the wider large intestine. Both have several sections.
Small intestine
It is divided from top to bottom into the duodenum, jejunum and ileum. You can find out more about this in the article on the small intestine.
Large intestine
It is divided from top to bottom into the cecum (with appendix), colon and rectum (rectum with anus). Read more about this in the article on the large intestine.
How long is the intestine in total?
The total length of the intestine is around eight meters. Five to six meters of this is the small intestine and the rest is the large intestine.
What is the function of the intestine?
The meter-long digestive tract is not only responsible for the chemical breakdown of food, the intake of food components into the body (absorption) and the excretion of food residues via the anus. It also acts as a barrier to pathogens and plays an important role in regulating the water balance: The intestine can reabsorb and also excrete large amounts of fluid.
Small intestine function
Additional glandular secretions, which originate from the intestinal wall itself, participate in digestion. After the food has been broken down and digested in the mouth and stomach, the food components are broken down into small components throughout the small intestine and absorbed into the blood:
Carbohydrates are broken down into simple sugars (monosaccharides), proteins are broken down into the individual amino acids, and fats are broken down into glycerol and free fatty acids. After being absorbed into the blood, these nutrients are first transported to the liver via the portal vein. This is the central metabolic organ.
Other substances are also absorbed into the body in this way, such as vitamins and minerals.
Large intestine function
Food components that the body does not need or cannot utilize end up in the large intestine. The muscle wall pushes this pulp with wave-like (peristaltic) movements through the individual sections to the exit (anus). On its way, the stool (feces) is thickened by dehydration. Mucus secreted by the intestinal wall makes it slippery.
The work of the intestinal bacteria also produces gases and substances that give the thickened food pulp its color and smell. This stool, which is no longer usable, is ultimately expelled via the anus.
Depending on the type of food consumed, it takes 33 to 43 hours from ingestion to defecation.
Where is the intestine located?
It fills almost the entire abdominal cavity below the stomach. The duodenum is located in the upper abdomen directly below the stomach, the jejunum joins it on the upper left and the ileum on the lower right. The numerous loops of jejunum and ileum are collectively referred to as the convoluted duodenum. It is framed, so to speak, by the colon. This then opens outwards at the bottom with the rectum and anus.
What problems can the bowel cause?
In a duodenal ulcer, a more or less large area of the mucous membrane in the duodenum is damaged. A gastric ulcer (ulcus ventriculi) often occurs in addition. Men are more frequently affected than women. In most cases, the cause of the ulcer is an infection with the “stomach germ” Helicobacter pylori.
Irritable bowel syndrome (irritable colon) manifests itself in chronic symptoms such as diarrhea and/or constipation, flatulence and abdominal pain. An organic cause cannot be determined. The disease mainly affects women.
Crohn’s disease and ulcerative colitis are chronic inflammatory bowel diseases (IBD). Crohn’s disease can affect the entire digestive tract (from the oral cavity to the anus). The inflammatory process in ulcerative colitis usually begins in the rectum and spreads to the colon.
In people who suffer from haemorrhoids, a vascular cushion in the anal canal is abnormally dilated. Possible symptoms include bright red traces of blood on the stool or toilet paper, pressure pain, burning or itching in the anus. In advanced stages, the stool can no longer be held back. Risk factors for hemorrhoids include repeated forceful straining during bowel movements, a low-fibre diet, pregnancy and weak connective tissue.
Diverticula are outward protrusions of the intestinal wall. If several diverticula form next to each other, doctors refer to this as diverticulosis. The protrusions can become inflamed (diverticulitis). Sometimes they also burst, in which case the inflammation can spread to the peritoneum. Diverticulitis is treated with antibiotics. Sometimes the inflamed diverticula also have to be surgically removed.